The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Brushless DC (direct current) motors comprise a multi-phase electric motor (hereinafter the motor) and a motor driver circuit. In operation, the motor driver circuit transforms a DC power source into a plurality of AC (alternating current) signals which are used to drive the motor. The motor driver circuit generates the AC signals according to a position of a rotor of the motor with respect to one or more of a plurality of coils of the motor.
Back-EMF detection may be used to determine the position of the rotor with respect to the coils. However, the back-EMF of the motor may be weak and unreliable for use in determining the rotor position when the rotor is being started. Inductive sensing may be used to determine the position of the rotor when the motor is being started. An effective inductance of each coil of the motor varies depending on the position of the rotor relative to each coil. During inductive sensing, voltage pulses are applied to the each of the plurality of coils, and the position of the rotor is determined by analyzing a slope of a current induced within each coil